MACH
®
Gas Fired Boiler
11
Circ Pump Relay w/Delay Off
- This output is enabled when there is a call for heat. When the call for heat is
removed, the output remains enabled for a period of time. This output provides 120VAC 0.5Amp service to TB2-13.
The neutral for this circuit is provided on TB2-6.
Damper Relay
- This output is enabled when the call for heat is enabled. This output provides 120VAC service to
TB2-14. The neutral for this circuit is provided on TB2-7. This circuit is for pilot duty only.
Master Alarm Relay
– This contact closes in the event of an alarm output from the boiler control, connecting TB2-15
and TB2-16.
Flame Detected Relay
– This contact closes whenever the boiler is firing, connecting TB2-17 and TB2-18.
3.4.2 Low Voltage (TB1) Terminal Block
Enable/Disable
– TB1-1 and TB1-2 are used for enabling the boiler. Closing this circuit allows the boiler to run.
Opening this circuit prevents the boiler from running. This circuit is energized by the boiler. It has a 24VAC potential.
Devices connected to these terminals must be rated for 24VAC
External Interlock
– TB1-3 and TB1-4 are used for attachment of an additional field safety device to the boiler control
circuit. Closing this circuit allows the boiler to run. Opening this circuit prevents the boiler from running. This circuit is
energized by the boiler with a 5V potential. Devices connected to these terminals must be rated for 5V.
Outdoor Temp Sensor
– TB1-5 and TB1-6 are connected to the outdoor temperature sensor. The temperature
control must be programmed to run an outdoor air schedule. The outdoor air sensor and programming help are
available from the local Harsco Industrial, Patterson-Kelley Representative. This circuit is energized by the boiler with
a 5V potential. The temperature sensor must be a NTC having 12k@25°C.
DHW Stat/Sensor
– TB1-7 and TB1-8 are connected to the DHW temperature sensor or thermostat. This circuit is
energized by the boiler with a 5V potential. The temperature sensor must be a NTC having 12k@25°C.
Header Temp Sensor
– TB1-9 and TB1-10 are connected to the header temperature sensor. This circuit is
energized by the boiler with a 5V potential. The temperature sensor must be a NTC having 12k@25°C.
DHW Flow Switch
– TB1-11 is energized by the boiler with a 5V potential. This circuit connects through a flow switch
on the domestic side of a domestic hot water system. The flow switch should close upon flow to provide a closed
circuit back to TB1-12.
Analog Input
– Remote signal for controlling the boiler. The boiler can be operated in a remote setpoint or a remote
firing rate control mode. Input 0-10VDC signal on TB1-13 only. The 0V Analog Input is provided on TB1-14. The
temperature control must be programmed to run with the analog input.
MODBUS
®
– TB1-17 and TB1-18 are used for connecting a MODBUS
®
building management system. (See the
ENVI
®
Control Advanced Users Guide for more information)
Cascade
– TB1-19 and TB1-20 are used to connect between boilers that are part of a Master/Member Network. Up to
24 boilers may be connected together. (See the ENVI
®
Control Advanced Users Guide for more information)
